March 12, 2016

New Fuel Cell Design Powered by Graphene-wrapped Nanocrystals

 A powdery mixture of graphene-wrapped magnesium nanocrystals, produced at
Berkeley Lab, is stable in air. The mixture’s energy properties show promise for use
in hydrogen fuel cells. (Eun Seon Cho/Berkeley Lab)

(March 12, 2016)  Berkeley Lab innovation could lead to faster fueling, improved performance for hydrogen-powered vehicles

Hydrogen is the lightest and most plentiful element on Earth and in our universe. So it shouldn’t be a big surprise that scientists are pursuing hydrogen as a clean, carbon-free, virtually limitless energy source for cars and for a range of other uses, from portable generators to telecommunications towers—with water as the only byproduct of combustion.

While there remain scientific challenges to making hydrogen-based energy sources more competitive with current automotive propulsion systems and other energy technologies, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new materials recipe for a battery-like hydrogen fuel cell—which surrounds hydrogen-absorbing magnesium nanocrystals with atomically thin graphene sheets—to push its performance forward in key areas.

Thin sheets of graphene oxide (red sheets) have natural, atomic-scale defects that
allow hydrogen gas molecules to pass through while blocking larger molecules
such as oxygen (O2) and water (H2O). Berkeley Lab researchers encapsulated
nanoscale magnesium crystals (yellow) with graphene oxide sheets to produce
a new formula for metal hydride fuel cells. (Jeong Yun Kim)

The graphene shields the nanocrystals from oxygen and moisture and contaminants, while tiny, natural holes allow the smaller hydrogen molecules to pass through. This filtering process overcomes common problems degrading the performance of metal hydrides for hydrogen storage.

These graphene-encapsulated magnesium crystals act as “sponges” for hydrogen, offering a very compact and safe way to take in and store hydrogen. The nanocrystals also permit faster fueling, and reduce the overall “tank” size.

“Among metal hydride-based materials for hydrogen storage for fuel-cell vehicle applications, our materials have good performance in terms of capacity, reversibility, kinetics and stability,” said Eun Seon Cho, a postdoctoral researcher at Berkeley Lab and lead author of a study related to the new fuel cell formula, published recently in Nature Communications.

In a hydrogen fuel cell-powered vehicle using these materials, known as a “metal hydride” (hydrogen bound with a metal) fuel cell, hydrogen gas pumped into a vehicle would be chemically absorbed by the magnesium nanocrystaline powder and rendered safe at low pressures.

journal reference (Open Access) >>